Swash plate pump



Nov. 8, 1955 LUCIEN 2,722,890

SWASH PLATE PUMP Filed May 26, 1954 III II 1A 13 i E 1a 21 6- .21 2 $14 United States Patent Ofiice SWASH PLATE PUMP Ren Lucien, Paris, France, assignor to Societe dlnventions Aerouautiques et Mecaniques S. I. A. M., Fribourg, Switzerland, a corporation of Switzerland Application May 26, 1954-, Serial No. 432,574 Claims priority, application France November 6, 1953 2 Claims. (Cl. lul -42) This invention comprises improvements in swash plate pumps.

Numerous embodiments of pumps of this type are known, in which plungers are movable in cylinders with which they form individual pumps and are actuated by a swash plate rotating relatively to the plungers about a central axis and inclined to said axis, the said plungers being returned by means of one or more springs.

Attempts have also been made to make such pumps in which the delivery is automatically dependent on the pressure in the delivery pipe of the pump.

The present invention comprises a swash plate pump of a particularly simple construction, having the following characteristics:

1. One or more ports are provided in the walls of the cylinders which are normally closed by an auxiliary piston valve subject at one end to the delivery pressure and at the other to the opposing action of a spring, these ports being uncovered by said piston valve when the pressure exceeds a limiting value and then bring the cylinders into communication with a return port to the suction side of the pump, thus ensuring automatic regulation as a function of the delivery pressure.

2. Return movement of the plungers, after their delivery stroke, is brought about, not by the intervention of springs but by an oscillating plate, mounted by a ball-and-socket joint on a rod forming an extension of the driving shaft, which plate engages abutments behind the plunger heads.

One embodiment of the invention will now be described by way of example, reference being made to the accompanying drawings, in which:

Figure 1 is a longitudinal section through the axis of the driving shaft of the pump; and

Figure 2 is a detail of a modification.

Referring to Figure 1, the body 1 of the pump comprises two compartments 2 and 3 provided respectively with a suction port 4 and a delivery port 5, the compartment 3 also having a port 6 in communication with the suction reservoir from which the port 4 draws.

Round the chamber 3 and equidistant from the axis of the pump are arranged a number of cylinders 7 (of which only one appears in the drawing) in which are plungers 8, each having a head 13 at one end and a cylindrical cavity 9 at the other end, the latter communicating with the side of the plunger through a transverse port 10.

A swash plate 11 is rigidly secured to a driving shaft 12 and inclined in relation thereto. The swash plate bears on the heads 13 of the plungers, which have a suitably convex profile. A plate 14 supported by a rod 15 forming an extension of the shaft 12, engages behind the heads of the plungers; it contains orifices 16 through which the plungers pass.

The plate 14 is supported on the rod 15 by means of a ball joint member 17 and flange 18 and it is machined in the centre so as to have a spherical surface of the same diameter as the ball member 17. The spherical portion of 2,722,890 Patented Nov. 8, 1955 the plate 14 has suflicient clearance at the top to permit it to oscillate about the centre of the sphere to the extent required by the stroke of the plungers.

Each time the shaft 12 rotates, each plunger makes a corresponding reciprocating movement in its cylinder, being urged downwards by the plate 11 and urged back in the opposite direction by the plate 14.

If one of the plungers 8 is assumed to be in its uppermost position as shown in Figure 1, then the liquid enters the cylinder 7 of said plunger through the port 10. The plate 11, as it turns, forces the plunger down into the cylinder, thus closing the port 10. Thus put under pressure, the liquid causes the opening of a valve 19 against the action of the spring 20; the pumped liquid passes through the chamber 3 and leaves by the delivery port 5. All the plungers act in the same manner as the plate 11 rotates.

Automatic regulation of the delivery is ensured in the following manner:

In the chamber 3 there is housed a differential piston valve 21, the stem of which is hollow and the head of which is pierced by a port 22. It follows that the delivery pressure obtaining in the chamber 3 urges the valve 21 downwards against the pressure of a spring 23. When the delivery pressure exceeds a certain limit, the valve 21, compressing the spring, opens relief ports 24 provided in the wall which separates the chamber 3 from the cylinder bores 7. The latter are then brought into communication with the return port 6 to the reservoir. The individual pumps are thus wholly or partially by-passed and no longer deliver fully to the delivery circuit through port 5, until the pressure has dropped in the delivery pipe. The passage from one state to the other takes place gradually, the ports 24 being small, and uncovered or covered progressively.

In the modification illustrated in Figure 2, the rod 15, instead of being rigidly secured to the shaft 12, is mounted to slide thereon and is urged upwards by a spring 25. This arrangement enables the plate 14 to oscillate even if a piston refuses to rise completely in its return stroke, as a result of seizure. The risk of fracture or deformation under abnormal loads is thus avoided.

We claim:

1. A pump comprising a pump body having a plurality of separate pump cylinder bores, a pumping plunger in each of said bores, an admission chamber for the fluid to the said cylinder bores, an admission port thereto, a delivery chamber for fluid from the cylinder bores having a delivery port therefrom, a valve bore in said delivery chamber, a piston valve movable therein, a spring acting on one face of said piston valve; means to admit on the other face the pressure in the delivery chamber; an outlet port for the fluid in said valve bores; in the wall of each of the said cylinder bores at least one relief port between said cylinder bore and said valve bore, said relief ports being closed by said piston valve with the compression of said spring less than a predetermined value and being opened above said value.

2. A pump as claimed in claim 1 in which the said piston valve is a differential piston valve having a larger face exposed to the action of the pressure of the fluid in the delivery chamber and a smaller face exposed to said pressure and the action of said spring.

References Cited in the file of this patent UNITED STATES PATENTS 

